Method and/or system for determining blood glucose reference sample times

ABSTRACT

Subject matter disclosed herein relates to monitoring and/or controlling blood glucose levels in patients. In particular, times for obtaining metered blood glucose samples of a patient may be altered based, at least in part, on a blood glucose level of said patient observed from a blood glucose sensor.

This application is a continuation of U.S. patent application Ser. No.16/559,416, filed 3 Sep. 2019, which is a continuation of U.S. patentapplication Ser. No. 15/268,063, filed 16 Sep. 2016, which is acontinuation of U.S. patent application Ser. No. 13/171,244, filed 28Jun. 2011, which claims the benefit of U.S. Provisional PatentApplication No. 61/407,888, filed 28 Oct. 2010; U.S. patent applicationSer. No. 13/171,244, filed 28 Jun. 2011 and claims the benefit of U.S.Provisional Patent Application No. 61/361,876, filed 6 Jul. 2010, theentire content of each application is incorporated herein by reference.

BACKGROUND 1. Field

Subject matter disclosed herein relates to monitoring blood glucoselevels in patients.

2. Information

The pancreas of a normal healthy person produces and releases insulininto the blood stream in response to elevated blood plasma glucoselevels. Beta cells (P-cells), which reside in the pancreas, produce andsecrete insulin into the blood stream as it is needed. If p-cells becomeincapacitated or die, a condition known as Type 1 diabetes mellitus (orin some cases, if p-cells produce insufficient quantities of insulin, acondition known as Type 2 diabetes), then insulin may be provided to abody from another source to maintain life or health.

Traditionally, because insulin cannot be taken orally, insulin has beeninjected with a syringe. More recently, the use of infusion pump therapyhas been increasing in a number of medical situations, including fordelivering insulin to diabetic individuals or trauma patients. As of1995, less than 5% of Type 1 diabetic individuals in the United Stateswere using infusion pump therapy. Presently, over 7% of the more than900,000 Type 1 diabetic individuals in the U.S. are using infusion pumptherapy. The percentage of Type 1 diabetic individuals that use aninfusion pump is growing at a rate of over 2% each year. Moreover, thenumber of Type 2 diabetic individuals is growing at 3% or more per year,and growing numbers of insulin-using Type 2 diabetic individuals arealso adopting infusion pumps. Additionally, physicians have recognizedthat continuous infusion can provide greater control of a diabeticindividual's condition, so they too are increasingly prescribing it forpatients.

External infusion pumps are typically to control a rate of insulininfusion based, at least in part, on blood glucose measurements obtainedfrom metered blood glucose samples (e.g., finger stick samples) or fromprocessing signals received from a blood glucose sensor attached to apatient to provide sensor glucose measurements. By processing signalsfrom such a blood glucose sensor, a patient's blood glucose level may becontinuously monitored to reduce a frequency of obtaining metered bloodglucose sample measurements from finger sticks and the like. However,measurements of blood glucose concentration obtained from processingsignals from blood glucose sensors may not be as accurate or reliable asmetered blood glucose sample measurements obtained from finger sticksamples. Also, parameters used for processing blood glucose sensors forobtaining blood glucose measurements may be calibrated from time to timeusing metered blood glucose sample measurements as referencemeasurements obtained from finger sticks and the like. Accordingly,techniques for sensor-based continuous blood glucose monitoringtypically still incorporate metered blood glucose sample measurementsobtained from finger sticks and the like.

The so-called Yale Protocol provides one technique for determining afrequency for determining insulin infusion rates and time intervalsbetween metered blood glucose sample measurements for insulin infusiontherapy for a wide range of patients. Examples of the Yale Protocol maybe found in Goldberg P A, Siegel M D, Sherwin, R S, et al.“Implementation of a Safe and Effective Insulin Infusion Protocol in aMedical Intensive Care Unit”, Diabetes Care 27(2):461-467, 2004, andGoldberg P A, Roussel M G, Inzucchi S E. “Clinical Results of an UpdatedInsulin Infusion Protocol in Critically Ill Patients”, Diabetes Spectrum18(3):188-191, 2005. Regarding time intervals between metered bloodglucose sample measurements, the Yale Protocol may specify a timebetween metered blood glucose sample measurements based on a currentlyobserved blood glucose concentration and a rate of change at a lastreference check.

SUMMARY

Briefly, example embodiments may relate to methods, systems,apparatuses, and/or articles, etc. for obtaining a metered blood glucosesample measurement from a patient while monitoring a blood glucose levelin the patient by processing signals from a blood glucose sensor; anddetermining a time for obtaining a subsequent metered blood glucosesample measurement from the patient based, at least in part, on anindicator indicative of a reliability of the sensor. An alternativeimplementation may include providing an operator or attendant an optionto extend the time for obtaining the subsequent metered blood glucosemeasurement based in response to a prediction that an observed bloodglucose level of the patient is to reach a target range. Anotheralternative implementation may include providing the option in responseto an estimated lag between the blood glucose level and a measurement ofthe blood glucose level obtained at the sensor being less than athreshold. Another alternative implementation may include providing theoption at least in part in response to an observed variability in theblood-glucose level being below a threshold. Another alternativeimplementation may include providing the option at least in part inresponse to an observed change in the patient's insulin sensitivitybeing below a threshold. Another alternative implementation may includeproviding an operator or attendant an option to extend the time forobtaining the subsequent metered blood glucose measurement in responseto a duration that an observed blood glucose level of the patient hasbeen in a target range. Another alternative implementation may includeproviding an operator or attendant an option to extend the time forobtaining the subsequent metered blood glucose measurement by first timeextension in response to a duration that an observed blood glucose levelof the patient has been in a target range; and providing the operator orattendant an option to extend the time for obtaining another meteredblood glucose measurement following the subsequent metered blood glucosemeasurement by a second time extension longer in duration than the firsttime extension in response to an extended duration that an observedblood glucose level of the patient has been in a target range. Anotheralternative implementation may include determining the time forobtaining a subsequent metered blood glucose sample measurement based,at least in part, on a category of the patient. In a particularimplementation, the category of the patient is a surgical patient or adiabetic patient. Another alternative implementation may includedetermining the time for obtaining a subsequent metered blood glucosesample measurement based, at least in part, on an observed change ininsulin sensitivity of the patient. In another alternativeimplementation, the determined time for obtaining a subsequent meteredblood glucose sample measurement may be displayed to an attendant oroperator. In another alternative implementation, may include initiatingan alarm in response to the determined time for obtaining a subsequentmetered blood glucose sample measurement elapsing.

Other example embodiments may relate to methods, systems, apparatuses,and/or articles, etc. for obtaining a metered blood glucose samplemeasurement from a patient; observing a blood glucose level in thepatient by processing signals from a blood glucose sensor; anddetermining a time for obtaining a subsequent metered blood glucosesample measurement from the patient based, at least in part, on anearness of the observed blood glucose level to a target range. In aparticular implementation, the nearness of the observed blood glucoselevel to the target range may be determined based, at least in part, onwhether a prediction of the observed blood glucose level to be withinthe target range by a future time. In another alternativeimplementation, the nearness of the observed blood glucose level to thetarget range may be determined based, at least in part, on whether aprediction of the observed blood glucose level to be within the targetrange by a future time. In another alternative implementation, thenearness of the observed blood glucose level to the target range may bedetermined based, at least in part, on whether the observed bloodglucose level is within the target range. In another alternativeimplementation, the nearness of the observed blood glucose level to thetarget range may be determined based, at least in part, on a differencebetween observed blood glucose level and an upper or lower bound of thetarget range. Additionally, in yet another alternative implementation,an operator or attendant may be provided an option to extend the timefor obtaining the subsequent metered blood glucose measurement based inresponse to a prediction that an observed blood glucose level of thepatient is to reach the target range. In another alternativeimplementation, an option to extend the time for obtaining thesubsequent metered blood glucose measurement may be provided to anattendant or operator at least in part in response to an observedvariation in the blood-glucose level being below a threshold. In anotheralternative implementation, an option to extend the time for obtainingthe subsequent metered blood glucose measurement may be provided to anattendant or operator at least in part in response to an observed changein the patient's insulin sensitivity being below a threshold. In anotheralternative implementation, an option to extend the time for obtainingthe subsequent metered blood glucose measurement may be provided to anattendant or operator in response to a duration that an observed bloodglucose level of the patient has been in the target range. Anotheralternative implementation may include providing an operator orattendant an option to extend the time for obtaining the subsequentmetered blood glucose measurement by first time extension in response toa duration that an observed blood glucose level of the patient has beenin a target range; and providing the operator or attendant an option toextend the time for obtaining another metered blood glucose measurementfollowing the subsequent metered blood glucose measurement by a secondtime extension longer in duration than the first time extension inresponse to an extended duration that an observed blood glucose level ofthe patient has been in a target range.

In another aspect, one or more embodiments may be directed to anapparatus comprising: an interface to receive a metered blood glucosesample measurement from a patient; and a controller to monitor a bloodglucose level in the patient by processing signals from a blood glucosesensor; and determine a time for obtaining a subsequent metered bloodglucose sample measurement from the patient based, at least in part, onan indicator indicative of a reliability of the sensor. In onealternative implementation, the indicator indicative of the reliabilityof the sensor may be computed based, at least in part, on an observedtrend of signals generated by the blood glucose sensor. Such an observedtrend may comprise, for example, an observed change in sensitivity ofthe blood glucose sensor; at least one observed non-physiologicalanomaly; or an observed sensor drift.

In another aspect, one or more embodiments may be directed to anapparatus comprising: an interface to receive a metered blood glucosesample measurement from a patient; and a controller to: observe a bloodglucose level in the patient by processing signals from a blood glucosesensor; and determine a time for obtaining a subsequent metered bloodglucose sample measurement from the patient based, at least in part, ona nearness of the observed blood glucose level to a target range.

Other example embodiments are directed to methods, systems, apparatuses,and/or articles, etc. for: obtaining a metered blood glucose samplemeasurement from a patient; observing a blood glucose level in thepatient by processing signals from a blood glucose sensor; anddetermining a time for obtaining a subsequent metered blood glucosesample measurement from the patient based, at least in part, on anindicator indicative of a stability of the observed blood glucose level.In one alternative implementation, such an indicator indicative of astability of the observed blood glucose level may be based, at least inpart, on a length of time the observed blood glucose level is within atarget range. In another alternative implementation, the indicatorindicative of a stability of the observed blood glucose level may befurther based, at least in part, on a length of the target range and asize of the target range.

In another aspect, one or more embodiments may be directed to anapparatus comprising: means for obtaining a metered blood glucose samplemeasurement from a patient while monitoring a blood glucose level in thepatient by processing signals from a blood glucose sensor; and means fordetermining a time for obtaining a subsequent metered blood glucosesample measurement from the patient based, at least in part, on anindicator indicative of a reliability of the sensor.

In another aspect, one or more embodiments may be directed to anapparatus comprising: means for obtaining a metered blood glucose samplemeasurement from a patient; means for observing a blood glucose level inthe patient by processing signals from a blood glucose sensor; and meansfor determining a time for obtaining a subsequent metered blood glucosesample measurement from the patient based, at least in part, on anearness of the observed blood glucose level to a target range.

In another aspect, one or more embodiments may be directed to anapparatus comprising: means for obtaining a metered blood glucose samplemeasurement from a patient; means for observing a blood glucose level inthe patient by processing signals from a blood glucose sensor; and meansfor determining a time for obtaining a subsequent metered blood glucosesample measurement from the patient based, at least in part, on anindicator indicative of a stability of the observed blood glucose level.

In another aspect, one or more embodiments may be directed to an articlecomprising: a storage medium comprising machine-readable instructionsstored thereon which are executable by a special purpose computingapparatus to: process a metered blood glucose sample measurement from apatient while monitoring a blood glucose level in the patient byprocessing signals from a blood glucose sensor; and determine a time forobtaining a subsequent metered blood glucose sample measurement from thepatient based, at least in part, on an indicator indicative of areliability of the sensor.

In another aspect, one or more embodiments may be directed to an articlecomprising: a storage medium comprising machine-readable instructionsstored thereon which are executable by a special purpose computingapparatus to: process a metered blood glucose sample measurement from apatient; observe a blood glucose level in the patient by processingsignals from a blood glucose sensor; and determine a time for obtaininga subsequent metered blood glucose sample measurement from the patientbased, at least in part, on a nearness of the observed blood glucoselevel to a target range.

In another aspect, one or more embodiments may be directed to an articlecomprising: a storage medium comprising machine-readable instructionsstored thereon which are executable by a special purpose computingapparatus to: process a metered blood glucose sample measurement from apatient; observe a blood glucose level in the patient by processingsignals from a blood glucose sensor; and determine a time for obtaininga subsequent metered blood glucose sample measurement from the patientbased, at least in part, on an indicator indicative of a stability ofthe observed blood glucose level.

Other alternative example embodiments are described herein and/orillustrated in the accompanying Drawings. Additionally, particularexample embodiments may be directed to an article comprising a storagemedium including machine-readable instructions stored thereon which, ifexecuted by a special purpose computing device and/or processor, may bedirected to enable the special purpose computing device/processor toexecute at least a portion of described method(s) according to one ormore particular implementations. In other particular exampleembodiments, a sensor may be adapted to generate one or more signalsresponsive to a measured blood glucose concentration in a body while aspecial purpose computing device/processor may be adapted to perform atleast a portion of described method(s) according to one or moreparticular implementations based upon one or more signals generated bythe sensor.

BRIEF DESCRIPTION OF THE FIGURES

Non-limiting and non-exhaustive features will be described withreference to the following figures, wherein like reference numeralsrefer to like parts throughout the various figures:

FIG. 1 is a front view of example devices located on a body inaccordance with an embodiment.

FIG. 2A is a perspective view of an example glucose sensor system foruse in accordance with an embodiment.

FIG. 2B is a side cross-sectional view of a glucose sensor system ofFIG. 2A for an embodiment.

FIG. 2C is a perspective view of an example sensor set of a glucosesensor system of FIG. 2A for an embodiment.

FIG. 2D is a side cross-sectional view of a sensor set of FIG. 2C for anembodiment.

FIG. 3 is a cross sectional view of an example sensing end of a sensorset of FIG. 2D for an embodiment.

FIG. 4 is a top view of an example infusion device with a reservoir doorin an open position, for use according to an embodiment.

FIG. 5 is a side view of an example infusion set with an insertionneedle pulled out, for use according to an embodiment.

FIG. 6 is a cross-sectional view of an example sensor set and an exampleinfusion set attached to a body in accordance with an embodiment.

FIG. 7 is a plot of metered blood glucose sample measurements taken of apatient at time intervals based, at least in part, on whether apatient's blood glucose level is observed to be within a target range,according to an embodiment.

FIGS. 8 through 12 are plots illustrating an option to extend a time forobtaining a subsequent metered blood glucose sample measurement based,at least in part, on whether a patient's observed blood glucose level iswithin a target range, according to specific example embodiments.

FIGS. 13 through 15 are plots illustrating an option to extend a timefor obtaining a subsequent metered blood glucose sample measurementbased, at least in part, on a patient's predicted blood glucose level,according to specific example embodiments.

FIG. 16 is a plot illustrating adjustments to times between meteredblood glucose sample measurements in response to a hypoglycemic event.

DETAILED DESCRIPTION

In an example glucose control system environment, blood-glucosemeasurements may be obtained from a blood glucose sensor in any one ofseveral different specific applications such as, for example, aiding inthe application of insulin therapies in a hospital environment,controlling infusion of insulin in a patient-operated insulin infusionsystems, just to name a few examples. In particular applications, ablood glucose sensor may be employed as part of a system to controlinfusion of insulin so as to control/maintain a patient's blood glucosewithin a target range, thus reducing a risk that the patient's bloodglucose level transitions to dangerous extreme levels in the absence ofaction from the patient or treating attendant.

According to certain embodiments, example systems as described hereinmay be implemented in a hospital environment to monitor or controllevels of glucose in a patient. Here, as part of a hospital or othermedical facility procedure, a caretaker or attendant may be tasked withinteracting with a patient's glycemic management system to, for example:enter blood-glucose reference measurements into control equipment tocalibrate blood glucose measurements obtained from glucose sensors, makemanual adjustments to devices, and/or make changes to therapies, just toname a few examples. Alternatively, a patient or other non-medicalprofessional may be responsible for interacting with a closed-loopsystem to, for example, provide updated measurements of blood-glucoseconcentration obtained from metered blood glucose sample measurements orthe like.

In addition to diet and amounts of insulin taken, other factors mayaffect a patient's blood glucose level such as, for example, exercise,stress, whether the patient is diabetic or recovering from surgery, justto provide a few examples. Receiving too little insulin orunderestimating the carbohydrate content of a patient's meal may lead toprolonged hyperglycemia. Likewise, receiving too much insulin (e.g., byover-bolusing) for a given blood glucose level and/or meal may lead tohypoglycemia.

In particular applications, controlling acute hyperglycemia ofcritically ill patients is a high priority in ICU patient management.Particular treatment protocols may dictate closely managing patients'glucose levels by frequently checking glucose levels (e.g., usingmetered blood glucose sample measurements) according to a pre-determinedand fixed schedule, ordered by a physician. This pre-determined andfixed schedule for glucose checks may not bring about cost effectivepatient management, as patients' glucose levels are measured per routineprocedure instead of as appropriate according to the particular state ofthe patient. Given the dynamic nature of a critically ill patient'sglucose levels, it may be beneficial to tailor a frequency of bloodglucose measurements to an individual patient's state-dictating morefrequent checks while the patient's glucose is labile, and dictatingless frequent checks while the patient's glucose is relatively stable.This may not only improve patient care and outcomes, but may also moreefficiently utilize clinical staff's time and resources.

To address issues associated with a fixed glucose check schedule,particular embodiments are directed to a dynamic, patient responsiveglucose check timing process. In a particular implementation, continuousglucose monitoring may track patients' glucose levels on aminute-to-minute basis. Depending on a particular patient status definedby variables such as, for example, present sensor glucose level, sensorglucose rate of change, sensor glucose rate of increase or rate ofdecrease, sensor glucose 15-minute predicted value, sensor glucosereliability, and history of blood glucose reference checks, a time untila subsequent blood glucose reference sample may be determined.

Additionally, as a metered blood glucose sample measurement is received,a patient's attributes or status may be used to determine appropriatetimes to schedule a subsequent metered blood glucose sample measurement.If a sudden change has been made to a patient's therapy, includingchanges to nutritional intake status or medications, for example, thepatient may be more susceptible to glucose swings, suggesting morefrequent blood glucose reference checks. With a priori knowledge of anyimpending therapy changes, glucose swings may be predicted and averted.If clinical staff provides information to an adaptive time, indicatingthat a patient's glucose would soon rise or fall, the timer couldproactively adjust the recommended time to the next metered bloodglucose sample measurement to avoid excursions.

As pointed out above, the Yale Protocol provides one technique fordetermining a frequency for determining time intervals between meteredblood glucose sample measurements for use in insulin infusion therapyfor a wide range of patients and conditions. Here, a generalizedapproach to determining time intervals between metered blood glucosesample measurements to be short enough for addressing most, if not all,patients under most, if not all conditions. However, for some patientsunder some particular conditions, short time intervals between samplesconservatively determined according to the Yale Protocol may not benecessary to provide a safe and effective glycemic management, forexample. Here, depending on a particular application, obtaining meteredblood glucose sample measurements more frequently than necessary mayincur unnecessary inconvenience or cost. In a hospital environment, forexample, safely increasing a time interval between metered blood glucosesample measurements to be obtained by an attendant may reduce a numberof daily rounds for treating a particular patient. According to anembodiment, a metered blood glucose sample measurement may be obtainedfrom a patient in combination with a blood glucose level in the patientobserved from a continuous glucose monitoring sensor. In a particularimplementation, a metered blood glucose sample measurement may be takenas finger stick measurements, metered blood glucose samples, just toname a couple of examples. Sensor blood glucose measurements may beobtained from processing signals received from a blood glucose sensorattached to a patient. While metered blood glucose sample measurementsmay provide reliable and accurate measurements of a patient's bloodglucose level, these measurements are taken at discrete points in time.On the other hand, use of a blood glucose sensor allows for a continuousmonitoring of a patient's blood glucose level.

According to an embodiment, metered blood glucose sample measurementsobtained by an operator or attendant at discrete points in time may beused in combination with continuous glucose monitoring. In oneapplication, use of continuous glucose monitoring may allow for moreeffective management of a patient's glycemic state between metered bloodglucose sample measurements. In a particular implementation, on receiptof a metered blood glucose sample measurement from a patient, a time forobtaining a subsequent metered blood glucose sample measurement from thepatient may be based, at least in part, on a metric indicative of areliability of a sensor being used for continuous glucose monitoring. Inan alternative embodiment, a time for obtaining a subsequent meteredblood glucose sample measurement may be based, at least in part, onwhether the patient's current observed blood glucose level is within atarget blood glucose range.

In a particular implementation, the Yale protocol may be modified toconsider additional factors to more closely tailor determination of timeintervals between metered blood glucose sample measurements forparticular patients. By more closely tailoring these time intervals, acost or inconvenience associated with a continuous blood glucosemonitoring and related therapies may be reduced.

Further, in another particular application, as a patient recovers fromcritical illness and his glucose stabilizes, an adaptive timer mayobserve continuous glucose sensor trends and a history of metered bloodglucose sample measurements such that less frequent sample measurementschecks are dictated. The adaptive timer may automatically extend aduration until the next recommended metered blood glucose samplemeasurement, or it could prompt the clinical staff for their inputbefore adjusting any timing recommendation. For example, if a patient'ssensor glucose has stabilized within a pre-determined target range for apre-defined time duration, the Adaptive Timer for Blood GlucoseMeasurement can alert the clinical staff.

In a particular implementation, based, at least in part, on a review ofa patient's glycemic status, a recommendation of an extension of time toa subsequent metered blood glucose sample measurement may be provided toa clinician. This may enable tailored patient care and better use ofclinical staff's time to address issues as dictated by actual patientcondition.

Overview of Example Systems

FIGS. 1 through 5 illustrate example glucose control systems inaccordance with certain embodiments. Such glucose control systems may beused, for example, in controlling a patient's glucose level about atarget range as discussed above. It should be understood, however, thatthese are merely examples of particular systems that may be use forcontrolling a patient's glucose level about a target range and thatclaimed subject matter is not limited in this respect. FIG. 1 is a frontview of example devices located on a body in accordance with certainembodiments. FIGS. 2A-2D and 3 show different views and portions of anexample glucose sensor system for use in accordance with certainembodiments enabling continuous monitoring of a patient's blood glucoselevel. FIG. 4 is a top view of an example optional infusion device witha reservoir door in an open position in accordance with certainembodiments. FIG. 5 is a side view of an example infusion set with aninsertion needle pulled out in accordance with certain embodiments.

Particular example embodiments may include a sensor 26, a sensor set 28,a telemetered characteristic monitor 30, a sensor cable 32, an infusiondevice 34, an infusion tube 36, and an infusion set 38, any or all ofwhich may be worn on a body 20 of a user or patient, as shown in FIG. 1.As shown in FIGS. 2A and 2B, telemetered characteristic monitor 30 mayinclude a monitor housing 31 that supports a printed circuit board 33,battery or batteries 35, antenna (not shown), a sensor cable connector(not shown), and so forth. A sensing end 40 of sensor 26 may haveexposed electrodes 42 that may be inserted through skin 46 into asubcutaneous tissue 44 of a user's body 20, as shown in FIGS. 2D and 3.Electrodes 42 may be in contact with interstitial fluid (ISF) that isusually present throughout subcutaneous tissue 44.

Sensor 26 may be held in place by sensor set 28, which may be adhesivelysecured to a user's skin 46, as shown in FIGS. 2C and 2D. Sensor set 28may provide for a connector end 27 of sensor 26 to connect to a firstend 29 of sensor cable 32. A second end 37 of sensor cable 32 mayconnect to monitor housing 31. Batteries 35 that may be included inmonitor housing 31 provide power for sensor 26 and electrical components39 on printed circuit board 33. Electrical components 39 may sample asensor signal (not shown) and store digital sensor values (Dsig) in amemory. Digital sensor values Dsig may be periodically transmitted froma memory to a controller 12, which may be included in an infusiondevice.

With reference to FIGS. 1 and 4, a controller 12 may process digitalsensor values Dsig and generate commands for infusion device 34.Infusion device 34 may respond to commands and actuate a plunger 48 thatforces insulin out of a reservoir 50 that is located inside an infusiondevice 34. In an alternative implementation, glucose may also be infusedfrom a reservoir responsive to commands using a similar and/or analogousdevice (not shown). In alternative implementations, glucose may beadministered to a patient orally.

Also, controller 12 may collect and maintain a log or history ofcontinuous measurements of a patient's blood glucose level to, forexample, allow for characterization of a patient's glycemic trends. Forexample, and as illustrated below in particular example embodiments, ahistory of continuous blood glucose sensor measurements may enableprediction of a patient's blood glucose level at some time in thefuture.

In particular example embodiments, a connector tip 54 of reservoir 50may extend through infusion device housing 52, and a first end 51 ofinfusion tube 36 may be attached to connector tip 54. A second end 53 ofinfusion tube 36 may connect to infusion set 38 (e.g., of FIGS. 1 and5). With reference to FIG. 5, insulin may be forced through infusiontube 36 into infusion set 38 and into a body of a patient. Infusion set38 may be adhesively attached to a user's skin 46. As part of infusionset 38, a cannula 56 may extend through skin 46 and terminate insubcutaneous tissue 44 to complete fluid communication between areservoir 50 (e.g., of FIG. 4) and subcutaneous tissue 44 of a user'sbody 16.

As pointed out above, particular implementations may employ aclosed-loop system as part of a hospital-based glucose managementsystem. Given that insulin therapy during intensive care has been shownto dramatically improve wound healing and reduce blood streaminfections, renal failure, and polyneuropathy mortality, irrespective ofwhether subjects previously had diabetes (See, e.g., Van den Berghe G.et al. NEJM 345: 1359-67, 2001), particular example implementations maybe used in a hospital setting to control a blood glucose level of apatient in intensive care. In such alternative embodiments, because anintravenous (IV) hookup may be implanted into a patient's arm while thepatient is in an intensive care setting (e.g., ICU), a closed loopglucose control may be established that piggy-backs off an existing IVconnection. Thus, in a hospital or other medical-facility based system,IV catheters that are directly connected to a patient's vascular systemfor purposes of quickly delivering IV fluids, may also be used tofacilitate blood sampling and direct infusion of substances (e.g.,insulin, glucose, glucagon, etc.) into an intra-vascular space.

Moreover, glucose sensors may be inserted through an IV line to provide,e.g., real-time glucose levels from the blood stream. Therefore,depending on a type of hospital or other medical-facility based system,such alternative embodiments may not necessarily utilize all of thedescribed system components. The above described example components suchas sensor 26, sensor set 28, telemetered characteristic monitor 30,sensor cable 32, infusion tube 36, infusion set 38, and so forth, aremerely examples according to particular implementations and not intendedto limit claimed subject matter. For example, blood glucose metersand/or vascular glucose sensors, such as those described in co-pendingU.S. Patent Application Publication No. 2008/0221509 (U.S. patentapplication Ser. No. 12/121,647; to Gottlieb, Rebecca et al.; entitled“MULTILUMEN CATHETER”), filed 15 May 2008, may be used to provide bloodglucose values to an infusion pump control, and an existing IVconnection may be used to administer insulin to an patient. Otheralternative embodiments may also include fewer, more, and/or differentcomponents than those that are described herein and/or illustrated inthe accompanying Drawings.

As pointed out above, time interval between obtaining metered bloodglucose sample measurements from a patient may be determined, at leastin part, on whether the patient's blood glucose as observed from a bloodglucose sensor signals is within a target range. In one particularimplementation, a target range may be defined as a blood glucoseconcentration range where the patient's blood glucose level is at lowrisk of transitioning to dangerous extreme levels. For example, while apatient's blood glucose level is in such a target range, the risk ofhypoglycemia and hyperglycemia to the patient may be low even if thepatient, non-medical professional or medical professional is notobtaining frequent metered blood glucose sample measurements foreffective glycemic management.

According to an embodiment, a target range may be defined, at least inpart, by a target or set-point glucose level. Such a target or set-pointglucose level may be based, at least in part, on a patient's particularphysiology. For example, such a target or set-point glucose level may bedefined based, at least in part, on guidelines established by theAmerican Diabetes Association (ADA) and/or clinical judgment of apatient's physician. Here, for example, the ADA has recommended apre-prandial blood glucose concentration of between 80-130 mg/dl, whichis in the normal glycemic range. Alternatively, target or set-pointglucose level may be fixed at 120 mg/dl. In yet another alternative, atarget or set-point blood glucose concentration may vary over timedepending on particular patient conditions. It should be understood,however, that these are merely examples of a target or set-point bloodglucose concentration, and claimed subject matter is not limited in thisrespect.

As pointed out above, an attendant or operator in a hospital environmentmay obtain metered blood glucose sample measurements from a patientaccording to a Yale protocol, for example. As discussed below withreference to specific examples illustrated in FIGS. 7 through 13, a timefor obtaining a subsequent blood glucose reference sample may belengthened under certain circumstances.

FIGS. 7 through 16 are plots of a patient's blood-glucose level observedover a twenty-four hour period under different scenarios. A target rangefor a blood glucose level may be defined, for example, according to thepatient's particular physiology as discussed above. FIG. 7 illustratesblood glucose levels as measured by metered blood glucose samplemeasurements such as finger stick sample measurements shown as plotteddots. Metered blood glucose sample measurements are taken on hourlyintervals Q1 while the measured blood glucose level is above the targetrange, and then taken on two hour intervals Q2 following the thirdreference sample 102 in the target range (e.g., indicating that thepatient's blood glucose level as stabilized). Intervals between meteredblood glucose sample measurements may then remain at two hours while themeasured blood glucose is within the target range.

In particular embodiments, as described herein with particularnon-limiting examples, a time for obtaining a subsequent metered bloodglucose sample measurement may be determined based, at least in part, ona “nearness” of a patient's observed blood glucose level (e.g., fromcontinuous monitoring with a blood glucose sensor) to a target range. Inone aspect, an observed blood glucose level to a target range may bedetermined based, at least in part, on whether a prediction of theobserved blood glucose level is to be within the target range by afuture time. In another alternative implementation, a nearness of anobserved blood glucose level to the target range may be determinedbased, at least in part, on whether the observed blood glucose level iswithin the target range. In another alternative implementation, anearness of an observed blood glucose level to a target range may bedetermined based, at least in part, on a difference between observedblood glucose level and an upper or lower bound of the target range. Itshould be understood, however, that these are merely examples of how anearness of a patient's blood glucose level to a target range may bedetermined, and that claimed subject matter is not limited in thisrespect.

In a particular implementation, as an attendant or operator obtains ametered blood glucose sample from a patient (e.g., using a finger stickor other metered blood glucose measuring technique) the attendant oroperator may input or provide a metered blood glucose sample value to auser interface of a controller (e.g., controller 12). The controller maythen compute or determine a time for obtaining a subsequent meteredblood glucose sample measurement based, at least in part, on one or morefactors as discussed below. In alternative implementations, a controllermay automatically receive a metered blood glucose sample measurement. Asillustrated below in particular implementations, the controller may thenindicate a time for obtaining a subsequent metered blood glucose samplemeasurement by, for example, displaying a time, sounding an alarm to letthe operator or attendant know when to obtain the subsequent bloodglucose reference sample, etc.

In addition to using blood glucose reference samples for glycemicmanagement, in the particular techniques illustrated in FIGS. 8 through16 a controller may employ continuous glucose monitoring using a bloodglucose sensor as discussed above. While a blood glucose level asobserved from metered blood glucose sample measurements is shown asplotted dots, a blood glucose level as observed from continuous glucosemonitoring using a blood glucose sensor is shown as a continuous dottedline. In FIG. 8, like the scenario of FIG. 7, a patient's blood glucoseis measured with metered blood glucose samples on hourly intervals Q1beginning while the observed blood glucose level is above the targetrange, and then measured on longer intervals following the third bloodglucose sample measurement in the target range 104. However, withcontinuous glucose monitoring, a time for obtaining a subsequent meteredblood glucose sample measurement may be extended safely beyond thetwo-hour intervals Q2 to Q2+Q1(three hours) as shown. Here, responsiveto receipt of a metered blood glucose sample measurement 104, acontroller may give an attendant or operator an option to extend thetime for obtaining a subsequent blood glucose reference sample by anadditional hour. Here, the controller may display a message to theoperator or attendant indicating the option to extend the time forobtaining the subsequent measurement. In the particular example shown,an 18% reduction in a total number of blood glucose reference samplesover the particular example of FIG. 7 may be possible in the 24-hourperiod shown.

In FIG. 9 operation is similar to the scenario shown in FIG. 8 exceptthat, in response to receipt of a fourth metered blood glucose samplemeasurement 110 (or over five hours within the target range), acontroller may give an operator or attendant an option to extend a timefor obtaining a subsequent metered blood glucose sample measurement fromQ2+Q1 (or three hours) to Q2+Q2 (or four hours). This may allow for upto a 24% reduction in a total number of metered blood glucose samplemeasurements over the particular example of FIG. 7 in the 24-hour periodshown.

FIG. 10 illustrates operation which is similar to that of operationshown in FIG. 8 except that an operator or attendant is given an optionto extend a time for obtaining a subsequent metered blood glucose samplemeasurement from Q2 (two hours) to Q2+Q1 (three hours) after thepatient's blood glucose has been in a target range for only one hour.This may allow for up to a 24% reduction in a total number of bloodglucose sample measurements over the particular example of FIG. 7 in the24-hour period shown.

FIG. 11 illustrates operation which is similar to that of operationshown in FIG. 10, except that an operator or attendant is given anoption to extend a time for obtaining a subsequent metered blood glucosesample measurement from Q2 (two hours) to Q2+Q2 (four hours) after thepatient's blood glucose has been in a target range for one hour. Thismay allow for up to a 29% reduction in a total number of metered bloodglucose sample measurements over the particular example of FIG. 7 in the24-hour period shown.

FIG. 12 illustrates operation which is similar to that of operationshown in FIG. 11, except that an operator or attendant is given anoption to extend a time for obtaining a subsequent metered blood glucosesample measurement from Q2 (two hours) to Q2+Q2 (four hours) immediatelyafter as the patient's blood glucose has reached a target range (insteadof after being in the target range for one hour). This may allow for upto a 35% reduction in a total number of blood glucose samplemeasurements over the particular example of FIG. 7 in the 24-hour periodshown.

As illustrated above by example, a controller may allow an attendant oroperator to optionally extend a time for obtaining a subsequent bloodglucose reference sample under certain conditions. In these particularexamples, such conditions may include 1) that a sensor glucosemeasurement indicates that a patient's blood glucose level is observedto be within a target range and 2) a length of time that the patient'ssensor glucose measurement has been observed to be in the target range.In these particular implementations, accuracy or reliability of a bloodglucose sensor may also be also be used for determining whether anattendant or operator may optionally extend a time for obtaining asubsequent metered blood glucose sample measurement. In a particularimplementation, an additional condition for optionally extending a timefor obtaining a subsequent metered blood glucose sample measurement mayinclude a reliability indicator (RI), which may be expressed as anumerical value. Thus, conditions for optionally extending a time forobtaining a subsequent metered blood glucose sample measurement may beexpressed as follows:

-   -   1. Sensor blood glucose (SBG) level observed to be within        patient's target range;    -   2. SBG observed to be in patient's target range for more than a        threshold duration; and    -   3. a reliability indicator (RI) comprising a numerical value        expressing an indication of reliability of the blood glucose        sensor exceeds a threshold value.

In a particular implementation, a controller may impose any or all ofthe above identified conditions for determining whether an attendant oroperator may optionally extend a time for obtaining a subsequent meteredblood glucose sample measurement. In a particular implementation, an RInumerically expressing a reliability of a glucose sensor may be computedusing one or more techniques including, for example, analysis ofobserved trends in signals generated by the glucose sensor. Suchobserved trends may include, for example and without limitation, areduced sensitivity of the glucose sensor, observed non-physiologicalanomalies or sensor drift as described in U.S. Provisional ApplicationNo. 61/407,888, filed on Oct. 28, 2010, which is herein incorporated byreference in its entirety. It should be understood, however, that theseare merely examples of how a reliability indicator (indicative of areliability of a blood glucose sensor) may be computed or derived forthe purpose of determining a time for obtaining a subsequent meteredblood glucose sample, and that other indicators of reliability may beused.

In one aspect, a presence of a patient's SBG in a target range orduration that the patient's SBG is in the target range may be anindicator of a stability of the patient's blood glucose level. Inanother aspect, a size of the target range in combination with aduration that the patient's SBG is in the target range may be anindicator of stability of the patient's blood glucose level. It shouldbe understood, however, that these are merely examples of indicators ofstability of a patient's blood glucose level which may be used indetermining a time for obtaining a subsequent metered blood glucosesample, and that other indicators of stability may be used.

The particular examples illustrated in FIGS. 8 through 12 are directedto providing an operator or attendant with an option for extending atime for obtaining subsequent metered blood glucose sample measurementfrom a patient under certain conditions as discussed above (e.g.,including whether blood glucose sensor measurements indicate that thepatient's blood glucose level is in a target range). In these particularexample implementations, a controller may give an operator or attendantthe option to extend a time for obtaining a subsequent metered bloodglucose sample measurement if a patient's sensor blood glucose isobserved to be in a target range. FIGS. 13 through 15 are directed to analternative implementation in which a time for obtaining a subsequentmetered blood glucose sample measurement may be extended if a patient'ssensor blood glucose is observed to be trending toward a target rangebut prior to reaching the target range. In one example implementation,if upon receipt of a metered blood glucose sample measurement a bloodglucose level is predicted to be within a target range for a scheduledsubsequent measurement sample time, the subsequent sample time may beextended. Such a prediction of a patient's blood glucose level may bebased, at least in part, on a currently observed sensor blood glucoselevel in combination with an approximated first derivative of the sensorblood glucose level with respect to time. Furthermore, it is pointed outthat change in a blood glucose level as observed though continuousglucose monitoring over time may be reflected in a non-stationary timeseries signal with trend and seasonality. Here, signals representing anobserved blood glucose level may be non-stationary because of thestatistical nature of sensor signals may change at least in part due tophysiological change and many other factors. A trend in signalsrepresenting an observed blood glucose level may be at least partiallyaffected by glucose control and/or patient recovery. A seasonality insignals representing an observed blood glucose level may be affected, atleast in part, by a daily cycle of a patient's physiology. As such, anyone of several time series forecasting and predicting techniques may beimplemented for predicting a patient's blood glucose. Examples oftechniques which may be applied to blood glucose sensor signals forpredicting an observed blood glucose may be found in Terence C. Mills,Time Series Techniques for Economists, Cambridge University Press, 1990,Peter R. Winters, Forecasting Sales by Exponentially Weighted MovingAverages, Management Science 6 (3): 324-342 and Rob J. Hyndman, Anne B.Koehler, J. Keith Ord, Ralph D. Snyder, Forecasting with ExponentialSmoothing: The State Space Approach, Springer Series in Statistics,2008.

In other embodiments, a prediction of a patient's sensor blood glucoselevel may also be based, at least in part, on an observed blood glucosevariability. As such, while a patient's observed sensor blood glucoselevel may be within the patient's target range and significantlyseparated by upper and lower glucose threshold levels defining thetarget range, the patient's observed sensor blood glucose level maybegin fluctuating or destabilizing (e.g., cycling within the targetrange). This may lead to a prediction of an out of target event in anear-future timeframe. It has been observed under certain hospitalconditions, for example, that a patient's glucose variability mayincrease twenty-four hours prior to a hypoglycemic event.

Variability of a patient's blood glucose may be characterized using anyone of several techniques. It should be understood, however, thatclaimed subject matter is not limited to any particular technique forcharacterizing variability of a patient's blood glucose. One techniqueincludes determining a daily mean and standard deviation of a bloodglucose level as discussed in Krinsley J S, “Glycemic variability: Astrong independent predictor of mortality in critically ill patients”,Crit Care Med vol 36, no 11, p 3008-3013, 2008. Another technique mayinvolve a determination of whether an observed blood glucose level isabove an upper threshold and below a lower threshold over a twenty-fourhour period as discussed in Bagshaw S M, et al., “The impact of earlyhypoglycemia and blood glucose variability on outcome in criticalillness”, Crit Care Med vol 13, no 3, pR91, 2009. Another technique mayinvolve a determination of a mean absolute glucose change per hour(e.g., the magnitude and number of glucose cycles per hour) as discussedin Hermanides J, et al., “Glucose variability is associated withintensive care unit mortality”, Crit Care Med vol 38, no 3, p 838-842,2010. Techniques for characterizing blood glucose variability may beapplied to either a continuously monitored sensor blood glucose level ormetered blood glucose samples providing a sequence of discrete pointsfor computation. Using a continuously monitored blood glucose level,blood glucose variability may be characterized, at least in part, bymeasuring of a magnitude of, and timing between, peaks in an observedsensor blood glucose level. A patient's blood glucose level may also becharacterized, at least in part, by a spectral analysis (e.g., using aFourier transformation) including, for example, evaluation frequencypatterns of glycemic changes.

As shown in FIG. 13, metered blood glucose sample measurements are takenon hourly intervals Q1 until the fifth hour at metered blood glucosesample 130. Here, while the observed blood glucose level is above atarget range, a currently observed sensor blood glucose level and itsslope (e.g., apparent first derivative with respect to time) suggest atrend that the patient's blood glucose is imminently entering the targetrange (e.g., before the next scheduled blood glucose reference sample).Here, responsive to blood glucose reference sample 130, a controller mayextend a scheduled time for a subsequent metered blood glucose samplefrom Q1 (one hour) to Q2 (two hours). Responsive to the first meteredblood glucose sample measurement within the target range 132 taken atthe seventh hour, a controller may give an attendant or operator anoption to extend a time for a subsequent metered blood glucose samplemeasurement from Q2 (two hours) to Q2+Q1 (three hours). Operation shownin FIG. 14 is similar to that shown in FIG. 13 except that an operatoror attendant is given an option to extend a scheduled time for asubsequent metered blood glucose sample 136 from Q2 to Q2+Q2 (fourhours). Operation shown in FIG. 15 is similar to that in FIG. 14, exceptthat an attendant or operator is given the option to extend a time to asubsequent metered blood glucose sample measurement from Q1 (one hour)to Q2+Q2 (four hours) responsive to sample measurement 138 at the fifthhour, before receipt of any metered blood glucose sample measurementwithin the target range.

In a particular implementation, operation as illustrated in 13 through15, in response to receipt of a metered blood glucose sample measurementa controller may evaluate the following conditions in determiningwhether an attendant or operator is to be given an option to extend atime for obtaining a subsequent metered blood glucose samplemeasurement:

-   -   Metered blood glucose sample measurement value is close to a        high end of a target range (e.g., within 50.0 mg/dl);    -   Insulin infusion rate (if any) is expected to remain constant;    -   Patient's blood glucose at a subsequent scheduled blood glucose        reference sample time is predicted to be within the target        range;    -   RI exceeds a predetermined threshold;    -   Characterization of patient's glucose variability is below a        threshold; and    -   Limited change in the patient's insulin sensitivity.

In one implementation, a patient's insulin sensitivity may becharacterized by an observed or expected change in the patient's bloodglucose level in response to a dose of insulin. This may be computedfollowing each insulin dose by observing changes in blood glucose levelfollowing the dose. Alternatively, a patient's insulin sensitivity maybe computed over a particular time period (e.g., four hours, twelvehours, twenty-four hours). Here, it may be observed that an insulinsensitivity of a critically ill patient may change rapidly as a diseasestate and metabolism fluctuate and as different mediations may alterinsulin sensitivity. In one implementation, attendant or operator is tobe given an option to extend a time for obtaining a subsequent meteredblood glucose sample measurement at least in part in response toapplication of a threshold computed insulin sensitivity.

FIG. 16 illustrates an alternative implementation in which a conditiondictating more frequent metered blood glucose sample measurements may bedetected while the patient's sensor blood glucose is still observed tobe within a target range. Here, between metered blood glucose samplemeasurements 152 and 154, a continuous blood glucose monitoring systemprocessing blood glucose sensor measurements may observe a trendindicating that the patient's blood glucose level may imminentlytransition outside of a target range. As shown in the particular exampleof FIG. 16, at point 158 between the eleventh and twelfth hours an eventmay be triggered indicating a trend toward transitioning to ahypoglycemic state. In one implementation, this event may prompt ortrigger corrective action such as, for example, taking the patient offof insulin, starting intravenous dextrose or both. In an alternativeimplementation, blood glucose reference sample 156 in a hypoglycemicrange may trigger a state in which intervals between successive meteredblood glucose sample measurements are shortened (e.g., to 15 minutes asshown in FIG. 16 by the characters “Q15×4”)) until the blood glucoselevel returns to be safely within the target range.

As discussed above, one factor in determining whether to optionallyextend a time for a subsequent metered blood glucose sample includes adelay or lag between an actual blood glucose level and a sensor bloodglucose measurement. Ideally, a blood glucose sensor and associatedcomponent(s) would be capable of providing a real time, noise-freemeasurement of a parameter, such as a blood glucose measurement, that acontrol system is intended to control. However, in real-worldimplementations, there are typically physiological, chemical,electrical, algorithmic, and/or other sources of time delays that maycontribute to a sensor measurement to lagging behind an actual presentvalue. Also, as noted herein, such a delay may arise from, for instance,a particular level of noise filtering that is applied to a sensorsignal.

FIG. 6 is a cross-sectional view of an example sensor set and an exampleinfusion set that is attached to a body in accordance with anembodiment. In particular example implementations, as shown in FIG. 6, aphysiological delay may arise from a time that transpires while glucosemoves between blood plasma 420 and interstitial fluid (ISF). Thisexample delay may be represented by a circled double-headed arrow 422.As discussed above with reference to FIG. 1-3, a sensor may be insertedinto subcutaneous tissue 44 of body 20 such that electrode(s) 42 (e.g.,of FIGS. 3 and 4) near a tip of sensor 40 are in contact with ISF.However, a parameter to be measured may include a concentration ofglucose in blood.

Glucose may be carried throughout a body in blood plasma 420. Through aprocess of diffusion, glucose may move from blood plasma 420 into ISF ofsubcutaneous tissue 44 and vice versa. As blood glucose level changes,so may a glucose level of ISF. However, a glucose level of ISF may lagbehind blood glucose level 18 due, at least in part, on a duration for abody to achieve glucose concentration equilibrium between blood plasma420 and ISF. Some studies have shown that glucose lag times betweenblood plasma and ISF may vary between, e.g., 0.0 to 30.0 minutes. Someparameters that may affect such a glucose lag time between blood plasmaand ISF are an individual's metabolism, a current blood glucose level,whether a glucose level is rising or falling, combinations thereof, andso forth, just to name a few examples.

A chemical reaction delay 424 may be introduced by sensor responsetimes, as represented by a circle 424 that surrounds a tip of sensor 26in FIG. 6. Sensor electrodes may be coated with protective membranesthat keep electrodes wetted with ISF, attenuate the glucoseconcentration, and reduce glucose concentration fluctuations on anelectrode surface. As glucose levels change, such protective membranesmay slow the rate of glucose exchange between ISF and an electrodesurface. In addition, there may be chemical reaction delay(s) due to areaction time for glucose to react with glucose oxidase GOX to generatehydrogen peroxide and a reaction time for a secondary reaction, such asa reduction of hydrogen peroxide to water, oxygen, and free electrons.

Thus, an insulin delivery delay may be caused by a diffusion delay,which may be a time for insulin that has been infused into a tissue todiffuse into the blood stream. Other contributors to insulin deliverydelay may include, but are not limited to: a time for a delivery systemto deliver insulin to a body after receiving a command to infuseinsulin; a time for insulin to spread throughout a circulatory systemonce it has entered the blood stream; and/or by other mechanical,electrical/electronic, or physiological causes alone or in combination,just to name a few examples. In addition, a body clears insulin evenwhile an insulin dose is being delivered from an insulin delivery systeminto the body. Because insulin is continuously cleared from blood plasmaby a body, an insulin dose that is delivered to blood plasma too slowlyor is delayed is at least partially, and possibly significantly, clearedbefore the entire insulin dose fully reaches blood plasma. Therefore, aninsulin concentration profile in blood plasma may never achieve a givenpeak (nor follow a given profile) that it may have achieved if therewere no delay.

Moreover, there may also be a processing delay as raw analog sensorsignals are processed for obtaining continuous measurements of apatient's blood glucose concentration. Description of such a processingdelay contributing to a lag between a present blood glucoseconcentration and a blood glucose sensor measurement for example may befound in U.S. patent application Ser. No. 12/347,716, titled “Methodand/or System for Sensor Artifact Filtering,” filed on Dec. 31, 2008,and assigned to the assignee of claimed subject matter.

Unless specifically stated otherwise, as is apparent from the precedingdiscussion, it is to be appreciated that throughout this specificationdiscussions utilizing terms such as “processing”, “computing”,“calculating”, “determining”, “estimating”, “selecting”, “identifying”,“obtaining”, “representing”, “receiving”, “transmitting”, “storing”,“analyzing”, “associating”, “measuring”, “detecting”, “controlling”,“delaying”, “initiating”, “setting”, “delivering”, “waiting”,“starting”, “providing”, and so forth may refer to actions, processes,etc. that may be partially or fully performed by a specific apparatus,such as a special purpose computer, special purpose computing apparatus,a similar special purpose electronic computing device, and so forth,just to name a few examples. In the context of this specification,therefore, a special purpose computer or a similar special purposeelectronic computing device may be capable of manipulating ortransforming signals, which are typically represented as physicalelectronic and/or magnetic quantities within memories, registers, orother information storage devices; transmission devices; display devicesof a special purpose computer; or similar special purpose electroniccomputing device; and so forth, just to name a few examples. Inparticular example embodiments, such a special purpose computer orsimilar may comprise one or more processors programmed with instructionsto perform one or more specific functions. Accordingly, a specialpurpose computer may refer to a system or a device that includes anability to process or store data in the form of signals. Further, unlessspecifically stated otherwise, a process or method as described herein,with reference to flow diagrams or otherwise, may also be executed orcontrolled, in whole or in part, by a special purpose computer.

It should be noted that although aspects of the above systems, methods,devices, processes, etc. have been described in particular orders and inparticular arrangements, such specific orders and arrangements aremerely examples and claimed subject matter is not limited to the ordersand arrangements as described. It should also be noted that systems,devices, methods, processes, etc. described herein may be capable ofbeing performed by one or more computing platforms. In addition,instructions that are adapted to realize methods, processes, etc. thatare described herein may be capable of being stored on a storage mediumas one or more machine readable instructions. If executed, machinereadable instructions may enable a computing platform to perform one ormore actions. “Storage medium” as referred to herein may relate to mediacapable of storing information or instructions which may be operated on,or executed by, one or more machines (e.g., that include at least oneprocessor). For example, a storage medium may comprise one or morestorage articles and/or devices for storing machine-readableinstructions or information. Such storage articles and/or devices maycomprise any one of several media types including, for example,magnetic, optical, semiconductor, a combination thereof, etc. storagemedia. By way of further example, one or more computing platforms may beadapted to perform one or more processes, methods, etc. in accordancewith claimed subject matter, such as methods, processes, etc. that aredescribed herein. However, these are merely examples relating to astorage medium and a computing platform and claimed subject matter isnot limited in these respects.

Although what are presently considered to be example features have beenillustrated and described, it will be understood by those skilled in theart that various other modifications may be made, and equivalents may besubstituted, without departing from claimed subject matter.Additionally, many modifications may be made to adapt a particularsituation to the teachings of claimed subject matter without departingfrom central concepts that are described herein. Therefore, it isintended that claimed subject matter not be limited to particularexamples disclosed, but that such claimed subject matter may alsoinclude all aspects falling within the scope of appended claims, andequivalents thereof.

What is claimed is:
 1. A method comprising: determining a first glucosereference sample measurement for a patient based on signals from aglucose sensor; determining to extend a scheduled time for determining asecond glucose reference sample measurement based on a reliabilityindicator (RI) indicating a reliability of the glucose sensor satisfyinga first threshold; and in response to determining to extend thescheduled time, generating signals to provide a message indicating anoption to extend the scheduled time for obtaining the second glucoselevel reference sample measurement.
 2. The method of claim 1, whereinthe RI is based on one or more trends in the signals from the glucosesensor.
 3. The method of claim 2, wherein the one or more trendscomprise a reduced sensitivity of the continuous sensor.
 4. The methodof claim 2, wherein the one or more trends comprise one or more ofnon-physiological anomalies or sensor drift.
 5. The method of claim 1,wherein determining to extend the scheduled time is further based on anobserved glucose level being within a target range and wherein theobserved blood glucose level is based on the signals from the glucosesensor.
 6. The method of claim 1, wherein determining to extend thescheduled time is further based on an observed glucose level being in atarget range for more than a threshold duration and wherein the observedglucose level is based on the signals from the glucose sensor.
 7. Themethod of claim 6, wherein the RI is based on one or more trends in thesignals from the glucose sensor.
 8. The method of claim 6, wherein theone or more trends comprise a reduced sensitivity of the glucose sensor.9. The method of claim 8, wherein the one or more trends comprise one ormore of non-physiological anomalies or sensor drift.
 10. The method ofclaim 1, wherein the generating of the signals to provide the messagecomprises causing a display of the message indicating an option toextend the scheduled time for determining the second glucose referencesample measurement.
 11. An apparatus comprising one or more processorsconfigured to: determine a first glucose reference sample measurementfor a patient based on signals from a glucose sensor; determine toextend a scheduled time for determining a second glucose referencesample measurement based on a reliability indicator (RI) indicating areliability of the glucose sensor satisfying a first threshold; and inresponse to the determination to extend the scheduled time, generatesignals to provide a message indicating an option to extend thescheduled time for obtaining the second glucose level reference samplemeasurement.
 12. The apparatus of claim 11, wherein the RI is based onone or more trends in the signals from the glucose sensor.
 13. Theapparatus of claim 12, wherein the one or more trends comprise a reducedsensitivity of the glucose sensor.
 14. The apparatus of claim 12,wherein the one or more trends comprise one or more of non-physiologicalanomalies or sensor drift.
 15. The apparatus of claim 11, wherein, todetermine to extend the scheduled time, the one or more processors areconfigured to determine to extend the scheduled time based further on anobserved glucose level being within a target range and wherein theobserved glucose level is based on the signals from the glucose sensor.16. The apparatus of claim 11, wherein, to determine to extend thescheduled time, the one or more processors are configured to determineto extend the scheduled time based further on an observed glucose levelbeing within a target range for more than a threshold duration andwherein the observed glucose level is based on the signals from theglucose sensor.
 17. The apparatus of claim 16, wherein the RI is basedon one or more trends in the signals from the glucose sensor.
 18. Theapparatus of claim 16, wherein the one or more trends comprise a reducedsensitivity of the glucose sensor.
 19. The apparatus of claim 16,wherein the one or more trends comprise one or more of non-physiologicalanomalies or sensor drift.
 20. A computer readable storage mediumstoring instructions that, when executed, cause one or more processorsto: determine a first glucose reference sample measurement for a patientbased on signals from a glucose sensor; determine to extend a scheduledtime for determining a second glucose reference sample measurement basedon a reliability indicator (RI) indicating a reliability of the glucosesensor satisfying a first threshold; and in response to thedetermination to extend the scheduled time, generate signals to providea message indicating an option to extend the scheduled time forobtaining the second glucose level reference sample measurement.